Steam-based hvac system

ABSTRACT

Various methods and devices are provided for heating, cooling, and humidifying a space using a steam-based HVAC system having a steam source, at least one radiator located in a space to be heated or humidified, and a steam and condensate transfer apparatus extending between the steam source and the radiator. The steam and condensate transfer apparatus can have an inner tube configured for transferring steam disposed within an outer tube configured for transferring condensate and the inner tube can be centered within the outer tube such that the outer tube forms an annulus around the inner tube. The tube-in-tube conduit system or double-tube conduit system can take the form of Lego®-like components that can be fitted together to form the structure needed to deliver steam to light-weight flat-panel radiators located within all areas to be heated and/or humidified. The HVAC system can further include a cold air source for delivering cold air into the tube-in-tube conduit system to provide cold air to registers within spaces to be cooled. In one embodiment, the steam and condensate transfer apparatus can be formed from a thermoplastic, for example, polysulfone.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 11/459,023 filed on Jul. 21, 2006 and entitled“Steam Heating System with Tube-in-tube Steam Conduit,” which is herebyexpressly incorporated by reference in its entirety.

FIELD

The present invention generally relates to methods and devices forheating and cooling a space using a steam-based heating, ventilating,and air conditioning (HVAC) system.

BACKGROUND

Steam-based heating systems provide simple and reliable techniques forheating in a wide variety of industrial, commercial, and residentialapplications. Steam is delivered under low pressure of up to 2 psig at104 degrees Celsius to radiators that transfer the steam condensationheat to the surrounding air. Steam-based heating system have no movingparts, making for easy maintenance and a long life span. Systems havinga gas powered pilot thermocouple can also be electricity independent,which is a tremendous advantage for regions prone to electricityshortages, as well as in cold climates. Steam systems today, however,are considered somewhat obsolete due to problems associated withconventional methods and equipment used for transferring the steam andcondensate.

Lighter weight copper tubing cannot be used in steam-based systemsbecause the rapid heating by the steam flow will cause damage tosoldered joints. Instead, threaded thick-walled steel pipes areconventionally used, requiring periodic draining to remove rustparticles that form over time. Conventional steam heating systems arealso notoriously inefficient because temperature in a space is rarelymaintained at or near a desired set point. Typical systems employ athermostat in the most distant space to be heated which controls aboiler. Upon a call for heat from the thermostat, steam is generated inthe boiler. As the steam pressure increases, the steam enters the metalpiping system forcing air to vent through the thermostatic vent valveslocated on the radiators. Once the hot steam replaces the air in theradiators the valve is closed. The steam must heat and maintain themetal piping system at 214° F. in order to “make a path” to theradiators. The burner continues to function until the temperaturesetting of the thermostat is reached, at which point the burner isdeactivated.

Drawbacks of such conventional systems reside in the fact that metalpipes require a significant amount of heat to reach operatingtemperature. The pick up factor for steam heating pipes is in a range1.3-1.5, meaning there is a 30-50% lost heat “load” which laterdissipates through insulation into basements or walls, significantlylowering the efficiency of the system. To reduce the proportion of lostheat, massive cast iron radiators are employed for accumulating the heatin a space to be heated. Further, radiators within a space to be heatedcontinue to emit heat after the set point is reached and after theburner is deactivated. Such residual heat raises the temperature withinthe space beyond the desired set point. As a result, there is acontinuous “hunting” cycle wherein the temperature in the most distantspace continuously varies from a temperature below the set point to atemperature above the set point. This “hunting” cycle is worse in spacescloser to the boiler because the boiler is only stopped once the correcttemperature is reached in the most distant space. The closer the spaceis to a boiler, the faster it receives heat and the more overheated itmay become before the boiler shuts off. This can be partially remediedby setting the desired temperature below what is comfortable in the mostdistant room, but this increases the frequency of heating cycles and inturn, heat loss from system preheating.

In light of the above-mentioned drawbacks, hydronic and central airsystems have been the preferred choice in modern buildings. These newersystems, however, have their own drawbacks when compared withsteam-based systems. Hydronic systems are electrically dependent, havemoving parts which require maintenance, involve complicated energyconsumption metering and computations for residential buildings, and canbe damaged if use is discontinued during winter without draining thewater from the piping. On average, nearly 50 gallons of water must besupplied and pumped to deliver the same amount of heat as from eachgallon of water heated to vapor and then condensed to liquid in aradiator. Further, it is difficult and inefficient to pump the requiredvolume of water to upper floors in high-rise buildings. Typically,operating pressures for such a system are in the range of 30-100 psi,making hydronic systems more prone to leaks. Central air systems arealso electrically dependent and require large fans and bulky ductworkthat can be difficult to maintain. Ducts and the conditions within theducts created by central air systems can also encourage the growth offungus and bacteria. The air moving within the ductwork can circulatedust and odors that must be filtered. In addition, furnaces for bothhydronic and central air systems have a significantly shorter life spanthan boilers typically used in conventional steam-based systems.

Another major difference between steam-based heating systems andhydronic and forced-air systems is the method of heat transfer. Aradiator and/or baseboard is heating using both convection (air heating)and radiation (infrared wave emission). The higher the temperature ofthe radiator, the more heat is emitted by radiation. A typical steamheating radiator temperature is 104 degrees Celsius, which is higherthen 80-85 degrees Celsius for hydronic heating. This temperaturedifference makes a significant difference. When air is used forconvection heating, however, it is a poor heat conductor. Further, warmair tends to agitate and carry dust particles and will rise up andescape from a building. In contrast to convection heating, infraredradiation energy is transferred not through the air, but throughelectromagnetic waves, meaning, the air between the heating unit and the“recipient” does not warm up. A 52% energy savings was reported for anelectric radiant heating panel versus electrical baseboard heating.Radiant heating is natural, from a physiologically standpoint, becausethe human body absorbs up to 99% of radiant heat through the skin. Withradiant heat people are typically comfortable at lower airtemperatures—as much as 20° F. cooler—partially resulting in energysavings. The proposed steam-based heating system disclosed hereinembraces the advantages of electrical radiant heating but with asignificantly lower cost of fuel.

Thus, a modernized and improved steam-based system would be preferableboth to conventional steam-based systems as well as newer hydronic andcentral air systems. Accordingly, there is a need for an improvedsteam-based HVAC system.

SUMMARY OF THE INVENTION

The present invention generally provides for an HVAC system acting asteam-based heating system. The steam-based heating system can include asteam source, at least one radiator located in a space to be heated, anda steam and condensate transfer apparatus extending between the steamsource and the at least one radiator. In one embodiment, the steam andcondensate transfer apparatus can have an inner tube configured fortransferring steam disposed within an outer tube configured fortransferring condensate. The inner tube can be centered within the outertube such that the outer tube forms an annulus around the inner tube.The inner tube can be configured for delivering steam from the steamsource to the at least one radiator and the outer tube can be configuredto return condensate from the at least one radiator to the steam source.The steam and condensate transfer apparatus can generally be a system oftube-in-tube nipples, elbows, tees, adapters, and clamps extendingbetween the steam source and the at least one radiator.

In one embodiment, the HVAC system can further include a vent controllerapparatus positioned in proximity to a vent valve of the radiator and incommunication therewith. The steam source can be configured for frequentstops to allow the vent controller apparatus to redistribute steamflows. The vent controller can include a check-valve configured toregulate air into the radiator and a shut-off valve configured toregulate air out of the radiator. A temperature monitoring device can beconfigured to monitor a temperature of ambient air within the space tobe heated and to control the shut-off valve. In an embodiment, the steamsource can include a steam source controller and the temperaturemonitoring device can be configured to communicate information to thesteam source controller as to heating requirements based on thetemperature of ambient air within the space to be heated.

The radiator can be a light-weight flat panel radiator and it can bedivided into two or more sections, each section having its own ventvalve and vent controller independently controllable by the temperaturemonitoring device. In one embodiment, the steam source can be a boiler.In another embodiment, the steam and condensate transfer apparatus canbe formed from a thermoplastic, including but not limited topolysulfone. In further embodiments, the steam and transfer apparatuscan be formed using an extrusion process.

In another embodiment, the HVAC system can include a humidifierapparatus configured for increasing the humidity of the space to beheated. The humidifier apparatus can include a water reservoir and apaper screen in communication with the water reservoir. The paper screencan be configured to receive and hold water from the water reservoir andto contact hot air from the radiator to cause evaporation of the waterheld in the paper screen to increase humidity in the space to be heated.In one embodiment, the water reservoir can be in communication with theradiator via condensate tubing and can be configured to receivecondensate through the condensate tubing from the radiator. Thecondensate tubing can have first and second check valves disposedtherein between the radiator and the water reservoir. The first andsecond check valves can be configured to control a flow of condensateinto and out of the water reservoir.

In another embodiment, the HVAC system can include a cold air sourceconnected to the steam and condensate apparatus of the steam-basedheating system. The steam and condensate apparatus can be furtherconnected to at least one air register for cooling a space to be cooled.The air register can include a control valve and a temperaturemonitoring device configured to monitor a temperature of ambient airwithin the space to be cooled. The temperature monitoring device canfurther be configured to control a shut-off valve on an air register.The cold air source can be an absorption heat pump configured to receiveenergy from the steam source. The HVAC system can also include an airblower configured to transfer air into a mixing apparatus to throttlechilled water produced by the absorption heat pump. The mixing apparatuscan be configured to cool the air, remove dust, and remove excessmoisture. The mixing apparatus can be further configured to direct thecooled air into a separator configured to remove liquid water. Theseparator can be configured to direct the cooled air into the steam andcondensate transfer apparatus for delivery to the air register. Theliquid water can be configured to be filtered and returned to theabsorption heat pump.

In another embodiment, a steam and condensate transfer apparatus isprovided and can include a plurality of conduit sections fitted togetherto extend between a steam source and a radiator. The steam andcondensate transfer apparatus can be configured to transfer steam fromthe steam source to the radiator and to transfer condensate from theradiator to the steam source. Further, each section in the plurality ofconduit sections can be formed from an outer tube disposed around aninner tube. In particular, the outer tube can be configured to transfercondensate from the radiator to the steam source and the inner tube canbe configured to transfer steam from the steam source to the radiator.In one embodiment, the steam and condensate transfer apparatus can beformed from a thermoplastic material.

Methods are also provided and can include a method for heating a space.In one embodiment, the method can include heating water into steam andintroducing the steam into a tube-in-tube conduit system formed from athermoplastic material. The method can further include delivering steamto a radiator within a first tube of the tube-in-tube conduit system andreturning condensate from the radiator within a second tube of thetube-in-tube conduit system. The first tube can be disposed inside thesecond tube.

The method can also include monitoring a temperature of air in a spaceto be heated and delivery of the steam to the radiator can be controlledbased on the temperature of the air in the space to be heated and basedon a pressure in the tube-in-tube conduit system. The method can furtherinclude humidifying air in a space to be heated using condensate fromthe steam delivered to the radiator. Temperatures in a space to beheated can be routinely checked to redistribute steam flows as needed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates one embodiment of a steam-based HVAC system forheating using tube-in-tube conduit for steam and condensate transfer;

FIG. 2A illustrates an embodiment of the assembly of a nipple portion ofthe tube-in-tube conduit of FIG. 1, showing an inner tube and an outertube;

FIG. 2B is a side view and a cross-section of one embodiment of an innertube nipple in the tube-in-tube conduit of FIG. 1;

FIG. 2C is a side view and a cross-section of one embodiment of an outertube nipple in the tube-in-tube conduit of FIG. 1;

FIG. 2D is a side view of one embodiment of tube-in-tube elbow in thetube-in-tube conduit of FIG. 1;

FIG. 2E is a side view of one embodiment of a tube-in-tube tee for usein line branching of the tube-in-tube conduit of FIG. 1;

FIG. 2F is a side view of one embodiment of tube-in-tube end tee havingflexible tubing attached for connecting steam delivery tube andcondensate return tube to a radiator in the HVAC system of FIG. 1;

FIG. 3A illustrates an embodiment of the assembly of a shifted nippleportion of tube-in-tube conduit of FIG. 1, showing an inner tube and anouter tube;

FIG. 3B is a side view and a cross-section of one embodiment of ashifted inner tube nipple in the tube-in-tube conduit of FIG. 1;

FIG. 3C is a side view and a cross-section of one embodiment of ashifted outer tube nipple in the tube-in-tube conduit of FIG. 1;

FIG. 3D is a side view of one embodiment of a shifted tube-in-tube maleadapter in the tube-in-tube conduit of FIG. 1;

FIG. 3E is a side view of one embodiment of a shifted tube-in-tubefemale adapter in the tube-in-tube conduit of FIG. 1;

FIG. 3F is a side view of one embodiment of shifted tube-in-tube elbowin the tube-in-tube conduit with shift of FIG. 1;

FIG. 3G is a side view of one embodiment of a shifted tube-in-tube teein the tube-in-tube conduit of FIG. 1;

FIG. 4A is a representation of one embodiment of a valve system forcontrolling steam entrance into a radiator at the beginning of a heatingcycle in the steam-based HVAC system of FIG. 1;

FIG. 4B is a further representation of one embodiment of a valve systemfor controlling steam entrance into a radiator during the “breath-in”portion of a heating cycle in the steam-based HVAC system of FIG. 1;

FIG. 5 is a representation of a sectioned flat-panel radiator system foruse in the steam-based HVAC system of FIG. 1

FIG. 6A is a representation of a beginning of a heating cycle for in amethod for providing a humidifier that can be used in combination withthe steam-based HVAC system of FIG. 1;

FIG. 6B is a representation of condensate releasing into a container ina method for providing a humidifier that can be used in combination withthe steam-based HVAC system of FIG. 1;

FIG. 6C is a representation of condensate being prevented from goinginto a container in a method for providing a humidifier that can be usedin combination with the steam-based HVAC system of FIG. 1;

FIG. 6D is a representation of condensate draining from a container anda radiator and returning to a tube-in-tube annulus in a method forproviding a humidifier that can be used in combination with thesteam-based HVAC system of FIG. 1; and

FIG. 7 illustrates one embodiment of a steam-based HVAC system forcooling using tube-in-tube conduit.

DETAILED DESCRIPTION

Certain embodiments will now be described to provide an overallunderstanding of the principles of the structure, function, manufacture,and use of the devices and methods disclosed herein. One or moreexamples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting embodiments and that the scope ofthe present invention is defined solely by the claims. The featuresillustrated or described in connection with one embodiment may becombined with the features of other embodiments. Such modifications andvariations are intended to be included within the scope of the presentinvention.

The present invention provides methods and devices useful for heating,cooling, and humidifying a building using a steam-based HVAC systemhaving a steam source, at least one radiator located in a space to beheated, and a steam and condensate transfer apparatus extending betweenthe steam source and the radiator. The steam and condensate transferapparatus can include an inner tube configured for transferring steamdisposed within an outer tube configured for transferring condensate. Inone embodiment, a steam source produces and introduces steam into athermoplastic tube-in-tube conduit system to be distributed throughout abuilding. The tube-in-tube conduit system or double-tube conduit systemcan take the form of Lego®-like components that can be fitted togetherto form the structure needed to deliver steam to all rooms and/or areasof a building, as will be described in detail below. The tube-in-tubeconduit system provides particular advantages for a steam-based heatingand cooling system because air in the annulus provides insulation to theinner tube and the steam and condensate flows are separated during aheating cycle. The tube-in-tube structure allows steam to be transferredand delivered using a center tube within the conduit. The outer tube orannulus surrounding the inner tube can then be used for the condensatereturn. Alternatively or in addition, a separate line can be used forthe condensate return.

The steam system of the present invention can be used in any buildingand/or dwelling as needed. For example, the system can be used forresidential purposes in private homes. In addition, the system can beused in office and commercial buildings of all sizes and is particularlyefficient in high-rise buildings, as will be described below. For thepurposes of the descriptions herein, the term “building” will be used torepresent any home, dwelling, office building, educational facility,convention center, and commercial building, as well as any other type ofbuilding that can be heated, cooled, and/or humidified as will beappreciated by one skilled in the art.

In an embodiment, a steam source is provided for producing andintroducing steam into the steam-based HVAC systems described herein.The steam source can be any source known in the art capable of heatingwater to produce steam, including a boiler system located within thebuilding to be heated or cooled, and/or an external district heatingsystem capable of supplying steam from a location remote to thebuilding. In one embodiment, a single high-powered boiler can be used.Alternatively, one high-powered boiler can be replaced with a set ofsmaller capacity boilers that can be fired up individually or in agroup, depending on heating requirements. A steam source controller canroute the flows of steam throughout the building as needed as thecontroller receives temperature information from individual radiators,as will be described below. Further, a building's hot water supply canbe routed so as to supply the steam source with preheated hot water todecrease the response time of the steam source. A person skilled in theart will appreciate that any steam source capable of producing andintroducing steam into the systems described herein can be used asneeded. As will also be appreciated, the amount of steam produced andintroduced by the steam source will vary depending on the type, size,and requirements of the building.

FIG. 1 illustrates one embodiment of a steam-based HVAC system 10 inwhich a boiler 12 acts as the steam source. A steam supply line 16leaves the boiler 12 and transfers steam into an inner tube 13 of athermoplastic tube-in-tube conduit system beginning at a steam supplymain at 14. The steam is transferred through the tube-in-tube conduitsystem to radiators 20 located within areas or rooms of a building. Avalve system 22 located at each radiator 20, as will be described indetail below, can serve to control whether or not the radiator 20receives steam for heating. A condensate return 24 can transfer thecondensate from the radiator to an annulus or outer tube 26 of thetube-in-tube conduit system to be returned to the boiler 12.Alternatively or in addition, the condensate return 24 can directlytransfer the condensate to the boiler 12 through the wet return 30. Acheck-valve, explained below in reference to FIG. 5, positioned withinthe condensate returns can prevent the outgoing steam from entering theannulus. In the case in which the condensate is returned to the steamsource through a separate return line, well-insulated conduit can beused. A person skilled in the art will appreciate that any combinationof steam delivery tubing and return tubing can be used depending on thestructure and requirements of the building. An inset in FIG. 1illustrates one exemplary embodiment of a connection means between themetal steam main 14 and the plastic outer tube of tube-in-conduit. Asshown, a clamp or bracket system can provide the connection allowing forease of assembly. To reduce the tubes' thermal expansion difference, theinner plastic tube can extend significantly into the metal tube to lockair in annulus near joint. This technique will preserve connectionsbetween dissimilar materials against sharp heating by the steam.

As shown in FIG. 1, the conduit portions are fitted together so thatthey are continuously connected throughout the transition from sectionto section. The conduit can be formed from any thermoplastic polymers orplastics known in the art, and the inner and outer tubes can be formedfrom different materials and/or different grades of materials dependingon need and cost requirements. Any thermoplastic material having therequired heat characteristics can be used.

In one embodiment, polysulfones can be used to form the tube-in-tubeconduit. Polysulfones are particularly advantageous for use in thepresently described system because they are high-strength polymers ableto maintain their properties up to 150 degrees Celsius, therebyexceeding steam heating working temperatures of a maximum of about 104degrees Celsius. Further, polysulfones have high compaction resistanceand can therefore be used under high pressures, far exceeding pressuresassociated with steam delivery. Polysulfones can be molded, extruded,welded, and glued, making them easy to form into tubing for conduit andeasy to fit and secure together in assembling the required conduitsystem. In addition, polysulfones can be transparent, allowing for easyassessment of any problems in the system, as well as whether the systemneeds maintenance or cleaning.

A tube-in-tube structure formed from thermoplastics, such as thepolysulfones described above, provides many advantages lacking inconventional steam heating systems that use iron, steel, cast-iron orother metal piping with welded and/or soldered connections. The outertube/annulus provides a mechanical protective shield, insulation media,and pressure enclosure. Heat loss on the supply steam line is reduceddramatically using thermoplastics because less heat is required to heatand maintain the inner tube at 104 degrees Celsius. In addition, airlocked in the outer tube or annulus provides insulation to the steamline inner tube. Because of the reduced heat loss, there is lesscondensate that forms in the inner tube during the warm-up stage. Inaddition, the absolute roughness of thermoplastic tubing is orders ofmagnitude less than metal piping so that the linear velocity of thesteam can be higher. This allows for reduced diameter conduit providingthe same pressure drop as larger diameter metal piping. Further, theinner tube carrying the steam does not border any pressure differencemeaning the inner tube wall need only be thick enough to maintain thetube's shape. In the unlikely event that the inner tube carrying thesteam should form a leak, the steam will only be leaked into theenclosed annulus having the same pressure as the inner tube. Should aleak occur in the outer tube, steam will enter annulus and substituteair. A temperature indicator can be provided in the metal piping of thesteam main 14 to indicate if a leak ever occurs in the outer tube and toinitiate an emergency boiler stop. Finally, using thermoplasticseliminates the need to filter and drain rust particles from the steamand condensate lines.

In particular, in one embodiment shown in FIG. 2A-2F, the conduit partscan be connected by elbows, nipples, and tees, as well as all requiredadapters, reducers, and expanders. For example, FIG. 2A illustrates aconnection of the conduit's outer tube by nipple 50A and nipple 50Cillustrates an inner tube connection by way of an inner tube. FIG. 2Aillustrates the connection of both tubes simultaneously. The structureof nipples 50A, 50B, and 50C can also be seen in FIGS. 2A-2C. An innertube nipple 52 having flanges or fins 53 is provided within an exemplaryouter tube nipple 54. The flanges 53 are configured to hold the innertube within the outer tube and can also provide additional mechanicalstrength to the system. Alternatively or in addition, spacers can beused to center the position of the inner tube within the outer tube.FIG. 2D shows one exemplary embodiment of an elbow portion 56 oftube-in-tube conduit. FIG. 2E illustrates a double tube tee 58 that canbe used to branch a steam main line. FIG. 2F illustrates and exemplarytube-in-tube steam conduit end tee 60 that can connect an inner steamline and annulus to a radiator using flexible plastic/rubber tubing 62a, 62 b. In one embodiment, teflon-like materials can be used for theseflexible connections. In the illustrated embodiment, tube 62 a can beused to transfer steam to a radiator, while tube 62 b can be used totransfer condensate from the radiator into the tube-in-tube annulus orouter tube. A person skilled in the art will appreciate that anycombination of flexible tubing and tube-in-tube conduit can be used toconnect the conduit to a radiator.

An exemplary embodiment of shifted tube-in-tube fittings is illustratedin FIGS. 3A-3G. In the illustrated embodiments, the fittings are similarto those shown in FIGS. 2A-2F, but have an inner tube axially shiftedwithin an outer tube by an amount to allow for easier mating techniques.In particular, FIG. 3A illustrates three connections for nipples 70A,70B, and 70C. As can be seen, an inner tube 71 is axially shifted withrespect to an outer tube 72, although both inner and out tubes have thesame length. This particular structure allows for easier assemblybecause the inner tube can be glued or fitted together first, followedby the outer tube. Both approaches shown on FIG. 2 and FIG. 3 arecompatible; inner tube should be shorter then outer tube by the shiftlength to switch from tube-in-tube conduit having a shift totube-in-tube conduit without the shift. Correspondingly, the inner tubeshould be longer by a shift length for a switch in the other direction.FIG. 3B shows a shifted inner nipple 74 having fins or flanges 75 forstabilizing the inner tube within an outer tube nipple 76 shown in FIG.3C. FIGS. 3D-3G illustrates other forms of shifted tube-in-tube conduitincluding nipples, elbows, and tees.

As will be appreciated by those skilled in the art, any combination ofelbows, tees, nipples, and adapters can be used to build the steam-basedHVAC systems described herein within a building as needed. One pieceextruded tube-in-tube parts can be employed to improve strength and toease assembling. Inner tubes can be fixed to outer tubes by ribsprovisioned in the extrusion process. Fittings similar to the onesillustrated in FIGS. 3A-3G can be used for assembly. In one embodiment,the fittings can be formed by drilling or cutting a solid piece ofmaterial, such as a solid piece of polysulfone. To smooth flow turns andreduce pressure drop, connections having lesser angles can be used, aswell as the illustrated rectangular ones. Rectangular tubes can be usedas well to increase cross section and reduce pressure drop. Additionalinsulation surrounding the tube-in-tube conduit can be used for conduitsections located in external walls to reduce heat loss.

In the embodiment in which the conduit system is formed from multiplepieces and sections as described above, the conduit sections can bejoined or fitted together by any mechanism known in the art. Forexample, the outer tubes can be clamped and/or glued using snap/griphose clamps, compression nuts, and/or any other clamping mechanism knownin the art while the inner tubes can be glued or tightly fitted togetherusing low inner tube and fittings tolerances in which no glue isnecessary.

The thermoplastic tube-in-tube conduit embodiments disclosed thereinallows for more frequent boiler stops without significant heat loss.Therefore, a new control method can be employed having routine andmandatory steam source stops for “breath in” cycles. In particular,during a steam-heating cycle, air is pushed out of the radiator by theincoming steam so that the steam can enter the radiator. When the nextheating cycle starts, air in the radiator can be locked by a ventcontroller if the temperature in a heated space exceeds a temperaturesetting. In an exemplary embodiment, a single thermostat can regulatevent controllers on one or several radiators. Further, the thermostatcan control sections of the radiator to be excluded from heating cycledepending on temperature differences from a specified setting.Alternatively or in addition, independent temperature settings can beused for each heated space, and in each space heat consumption can beaccommodated independently. A steam source controller can also monitorthe signals from under heated spaces to determine the required heatload. Alternatively, the steam source load can be controlled during aheating cycle to keep the system pressure between operating pressure anda maximum system pressure. A person skilled in the art will appreciatethat the control method is not limited to that described above, but canvary as needed due to its simplicity and flexibility.

FIGS. 4A and 4B illustrate one exemplary valve system 22 having a ventcontroller 306 and a commonly used vent valve 304. The vent valve 304can employ any known principle (bimetal or bellow partially filled withalcohol and water mixture, etc), but generally allows air in and out ofthe radiator and shuts off when heated by steam. In the illustratedembodiment, the vent controller 306 is a separate unit that includes ashut-off valve 312 and a check valve 314. The vent valve will block thevent controller 306 from the hot steam, thereby protecting it. The ventcontroller 306 includes two lines associated with the shut-off valve 312and the check valve 314. As illustrated in FIG. 4A, during routine“breath-in” cycles, a vacuum is created in the radiators by condensedsteam and the air is pulled in through one directional check valve 314and cooled vent valve 304. When the next heating cycle begins and air ispushed out from the radiators, the check valve 314 will automaticallyshut off. The shut-off valve 312 is normally open and will stay opens ifthe temperature in the heated space is below a specific setting. If thetemperature in the heated space is above the setting, the shut-off valve312 will close, thereby locking air in the radiator and preventing steamfrom entering. Depending on the temperature settings, some radiators canbe excluded from the next heating cycle, thereby providing a moreefficient system. All shut off valves can be independently controlled,as well as manually adjustable if required. During routine “breath in”stops, the insulated inner tubes should lose a minimum amount of heatmaking overall heat loss reasonably low.

Gas fueled steam-based heating systems can be powered by a pilot lightthermocouple and will continue to heat all spaces in an electricityshortage. In this case, if electricity is lost, the controllers maybecome disabled, thereby preventing valves from locking the radiatorsbased on local temperature settings. In addition, if the shut-off valves312 are normally closed, they will lock all radiators, but can bemanually opened. In one embodiment, a combination of normallyclosed/open shut off valves can be used to provide heating of selectedspaces during an electricity shortage. A person skilled in the art willappreciate that any appropriate combination of vent valves and ventcontrollers can be used. Alternatively, a single controllable valvesynchronized with the steam source controller can be used to perform thejob of the vent controller 306.

Any radiators and/or baseboards known in the art can be used to transfersteam heat to a space within a building. A radiator or baseboard that isalready in place within a building can be retrofitted to work with thethermoplastic tube-in-tube conduit system by using, for example,flexible plastic connections made from, for example, Teflon, to joinolder radiator connections with the conduit. In one embodiment shown inFIG. 5, lightweight panel radiators can be used so that shorter stopsare required for the “breath-in” cycle because there is less volume tobe vented and the radiator cools quicker. A one directional check valveon the condensate return line can be used to lock air in annulus duringa heating cycle and to open during “breath in” cycle to flash condensateto the boiler.

The panel radiators can include corrugated plates to provide additionalsurface area for radiation, as well as a rigid structure. In anotherembodiment, the radiators can be divided into sections 110A, 110B, and110C, as shown in FIG. 5, with each section having its own ventcontroller. Depending on the temperature difference from what isrequired by the temperature setting, the temperature monitoring devicecan open more or less sections for steam access, allowing for moreprecise and flexible temperature control. Sectioned radiators haveadvantages because constant heat delivery to a particular space at apartial steam “load” is more efficient and comfortable than periodicheating at full steam load. The lightweight panel radiators areparticularly convenient because they can be placed anywhere within aspace as needed, including under windowsills, on walls, near ceilings,etc. In the embodiment illustrated in FIG. 5, all radiator sections110A, 110B, and 110C can be serviced by a single steam delivery line126, as well as a single condensate return line 128. Cross-section A-Aillustrates an example of the thinness of the flat panel radiators. Inaddition, for radiators located on or near the floor, perforatedthermoplastic covers can provide a safety shield for hot surfaces. Inone embodiment, the covers can be formed from polysulfone which istransparent to infrared waves, lightweight, washable and moldable.

In an embodiment, the system described above can also include humiditycontrol. A radiant heating system, as described above, does not dry thesurrounding air as much as a system based on convection heat. Even so,the system described herein can be optionally for humidity control.FIGS. 6A-6D illustrate one embodiment of a method for providing humiditycontrol at each individual radiator 20. In this particular embodiment,an additional line having check valve A is required to connect thecondensate return line to a condensate reservoir or container 400. FIG.6A illustrates the beginning of a heating cycle in which both checkvalves A and B are closed by pressure in the system. As condensate isformed within the radiator 20 during heating, check valve A ball floatsto allow the condensate to flow into a reservoir or container 400, asshown in FIG. 6B. Once condensate is pushed out from radiator, the checkvalve A closes again, as shown in FIG. 6C. As the heating cyclecontinues, water from the container 400 is absorbed into a wet paperscreen 402 illustrated in FIG. 6A. Water vapor is picked up throughevaporation as the hot air passes along the wet paper screen 402,thereby increasing the humidity in the space heated by the radiator 20.As the heating cycle finishes, the system cools, returning to vacuum andcausing check valves A and B to open and allow the water to drain fromthe container 400 and the radiator 20 and to return to the steam source,as shown in FIG. 6D.

The container 400 and the wet paper screen 402 can be contained within asingle unit covered by a plastic cover 406 to allow air to pass throughthe unit and absorb moisture from the wet paper screen 402. Freshoutside air can be directed through the plastic cover 406 to wet paperfor humidification. The rate of evaporation can be controlled bychanging the size of the section of the wet paper screen 402 that isexposed to the hot air of the radiator 20. The size of the paper screencan be manually or mechanically controlled by “rolling” the screen in orout of a holder. Pure distilled water is circulated through thehumidifier to prevent bacteria and fungus growth in the container 400.Water can be periodically added to the system to compensate for thewater that is evaporated into the surrounding air. Optionally, a floatlevel shut-off valve can be included within the container to preventwater overflow. A person skilled in the art will appreciate that theabove described valve system is exemplary in nature and variations canbe easily made to the system. More or fewer check valves can be includeddepending on system requirements, as well as a different valve systemall together if needed.

In one embodiment, the above described steam heating system can also beinclude an air conditioning system. Cooled air is supplied into thetube-in-tube apparatus and released through registers 524, as shown inFIG. 7. If a combined heating and cooling system is employed, it ispreferable to have all controlled valves (radiator vent controllers andthose located at the cold air distribution registers) normally closed.In this way, steam will not be released instead of cold air and cold airwill not enter radiators. Also, the system pressure can be checkedbefore supplying steam into a new, repaired, and/or modified system. Thesame temperature controllers used for heating operations can be appliedto open normally closed valves if the temperature rises above aspecified temperature setting.

While any cool air source or air cooling mechanism known in the art canbe used to supply chilled or cold air into the tube-in-tube conduit, inone embodiment, the steam flow normally used for heating is directed toprovide power or energy to an absorption heat pump 504, as shown in FIG.7. As shown, a cooling system 500 is provided having a boiler 502 forproviding steam to provide energy to an absorption heat pump 504. Watercan be chilled in the absorption heat pump 504 and throttled in a mixer506 into the fresh make-up/circulation air from a blower 526. Because ofthe huge contact surface, tiny droplets of cold water can quickly coolair and cause excessive moisture condensation. A separator 528 can thenremove excess moisture and dust particles from the cooled air and sendthe air into the tube-in-tube conduit. Valves 520 can control deliveryof the cold air at air registers positioned near the ceiling. Valvespositioned near the ceiling air registers 524 can control delivery ofcold air. The circulating water from separator 528 can be filtered andcooled again by the absorption heat pump 504.

Cold air from separator with 100% humidity may become too dry whenwarmed to room temperature. For example, air at 5 degrees Celsius with100% humidity will drop the humidity to 40% when this air is warmed to aroom temperature of 20 degrees Celsius. In this way, the cold air cancarry water droplets to increase the humidity of a space to acomfortable level. If the air is in the example is supersaturated, itcan carry suspended water particles into the air within a room to raisethe humidity from 40% to 70% when the air carrying the water particlesis heated to room temperature. In this way, 50% more cooling can beprovided from this evaporative cooling. By design, the tube-in-tubeconduit is perfectly provisioned for removing condensed moisturedroplets from the cold air should it condense within the tube. Smoothtube-in-tube conduit turns, low friction, and high linear velocitieswithin the tubing can facilitate water croplet carry over in a form ofmist. Therefore, control of supersaturated water from the separator canimprove humidity control and cooling efficiency.

FIG. 7 also illustrates integrated piping system schematic for airregisters 524 near the ceiling and three possible mounting positions forthe radiator, including a near the ceiling mounted radiator 530A, a wallmounted radiator 530B, and a radiator 530C with a separate condensatereturn line A person skilled in the art will appreciate that theradiator can be mounted anywhere within a space as needed. This systemprovides a particular advantage over conventional cooling systems.Instead of moving large volumes of air through bulky ducts, heatexchangers, and filters, only a fraction of clean, cold air or freshmake-up air is needed. Further, because relatively small air volumes areinvolved and the air is quickly cooled by throttling tiny droplets ofwater with very high contact surface area, the apparatus can becontained in a compact unit and can achieve high efficiencies whencompared with conventional systems.

The embodiments as described above are particularly efficient inhigh-rise buildings because pumped water is not required to heat upperfloors. Further, steam-based heating system maintenance is low becausethe system does not necessarily require moving parts. Theabove-described heating and cooling embodiments can also be used as amobile heating and cooling system. The low weight of the corrosion freetubing in combination with the low pressure requirements is ideal foruse in these environments. In an embodiment in which the system is usedwithin a ship, spare drinking water can be used or one small capacity“sacrifice” boiler can be designated to distill sea water for make-upwater. This also provides an alternative to the conventional use ofthermal liquid circulating pumps, valves, and bypasses. In addition,such systems provide better control flexibility and water logistics whencompared to the use of a thermal liquid. In another embodiment for usein closed air cycle systems like submarines, mines, space airconditioning by a cold water mist can be accompanied with carbon dioxideextraction.

A person skilled in the art will appreciate that the above-describedembodiments can be implemented in any number of ways and in any numberof systems requiring heating, cooling, and humidity control.Accordingly, the application is not to be limited by what has beenparticularly shown and described, except as indicated by the appendedclaims. All publications and references cited herein are expresslyincorporated herein by reference in their entirety.

1. An HVAC system, comprising a steam-based heating system, thesteam-based heating system comprising: a steam source; at least oneradiator located in a space to be heated; and a steam and condensatetransfer apparatus extending between the steam source and the at leastone radiator and having an inner tube configured for transferring steamdisposed within an outer tube configured for transferring condensate. 2.The HVAC system of claim 1, wherein the inner tube is centered withinthe outer tube such that the outer tube forms an annulus around theinner tube.
 3. The HVAC system of claim 1, wherein the steam andcondensate transfer apparatus comprises a system of inner and outertubes comprising tube-in-tube nipples, elbows, tees, adapters, andclamps extending between the steam source and the at least one radiator.4. The HVAC system of claim 1, further comprising a vent controllerapparatus positioned in proximity to a vent valve of the at least oneradiator and in communication therewith.
 5. The HVAC system of claim 4,wherein the steam source is configured for frequent routine stops toallow the vent controller apparatus to redistribute steam flows.
 6. TheHVAC system of claim 4, wherein the vent controller comprises acheck-valve configured to regulate air into the at least one radiatorand a shut-off valve configured to regulate air out of the at least oneradiator and a temperature monitoring device configured to monitor atemperature of ambient air within the space to be heated and to controlthe shut-off valve.
 7. The HVAC system of claim 6, wherein the steamsource further comprises a steam source controller and the temperaturemonitoring device is configured to communicate information to the steamsource controller as to heating requirements based on the temperature ofambient air within the space to be heated.
 8. The HVAC system of claim1, wherein the at least one radiator comprises a light-weight flat panelradiator.
 9. The HVAC system of claim 1, wherein the at least oneradiator is divided into two or more sections, each section having itsown vent valve and vent controller independently controllable by thetemperature monitoring device.
 10. The HVAC system of claim 1, whereinthe steam source comprises a boiler.
 11. The HVAC system of claim 1,wherein the steam and condensate transfer apparatus is formed from athermoplastic.
 12. The HVAC system of claim 1, wherein the steam andcondensate transfer apparatus is formed from polysulfone.
 13. The HVACsystem of claim 1, wherein at least one component of the steam andcondensate transfer apparatus is formed from a solid element using anextrusion process.
 14. The HVAC system of claim 1, further comprising ahumidifier apparatus configured for increasing the humidity of the spaceto be heated, wherein the humidifier apparatus comprises a waterreservoir and a paper screen in communication with the water reservoir,the paper screen being configured to receive and hold water from thewater reservoir, the paper screen being further configured to contacthot air from the at least one radiator to cause evaporation of the waterheld in the paper screen to increase humidity in the space to be heated.15. The HVAC system of claim 14, wherein the water reservoir is incommunication with the at least one radiator via condensate tubing andis configured to receive condensate through the condensate tubing fromthe at least one radiator, the condensate tubing having first and secondcheck valves disposed therein between the at least one radiator and thewater reservoir, the first and second check valves being configured tocontrol a flow of condensate into and out of the water reservoir. 16.The HVAC system of claim 1, further comprising a cold air source,wherein the cold air source is connected to the steam and condensateapparatus of the steam-based heating system, and wherein the steam andcondensate apparatus is further connected to at least one air registerin a space for cooling said space.
 17. The HVAC system of claim 16,wherein the at least one air register includes a control valve and atemperature monitoring device configured to monitor a temperature ofambient air within the space to be cooled and further configured tocontrol a shut-off valve.
 18. The HVAC system of claim 16, wherein thecold air source comprises an absorption heat pump, the absorption heatpump being configured to receive energy from the steam source.
 19. TheHVAC system of claim 18, further comprising an air blower configured totransfer air into a mixing apparatus to mix with throttled chilled waterproduced by the absorption heat pump, the mixing apparatus beingconfigured to cool the air, remove dust, and remove excess moisture. 20.The HVAC system of claim 19, wherein the mixing apparatus is furtherconfigured to direct the cooled air into a separator configured toremove liquid water, the separator being further configured to directthe cooled air into the steam and condensate transfer apparatus fordelivery to the at least one register, wherein the liquid water isconfigured to be filtered and returned to the absorption heat pump. 21.A steam and condensate transfer apparatus, comprising: a plurality ofconduit sections fitted together to extend between a steam source and aradiator and configured to transfer steam from the steam source to theradiator and to transfer condensate from the radiator to the steamsource, wherein each section in the plurality of conduit sections isformed from an outer tube disposed around an inner tube.
 22. The steamand condensate transfer apparatus of claim 21, wherein the outer tube isconfigured to transfer condensate from the radiator to the steam sourceand the inner tube is configured to transfer steam from the steam sourceto the radiator.
 23. The steam and condensate transfer apparatus ofclaim 21, wherein the plurality of conduit sections are formed from athermoplastic material.
 24. A method for controlling a temperature of aspace, comprising: heating a space by heating water into steam;introducing the steam into a tube-in-tube conduit system formed from athermoplastic material; and delivering steam to a radiator within afirst tube of the tube-in-tube conduit system and returning condensatefrom the radiator within a second tube of the tube-in-tube conduitsystem, wherein the first tube is disposed inside the second tube. 25.The method of claim 24, further comprising monitoring a temperature ofair in a space to be heated.
 26. The method of claim 25, whereindelivery of the steam to the radiator is controlled through a radiatorvent controller based on the temperature of the air in the space to beheated.
 27. The method of claim 24, wherein delivery of the steam to thetube-in-tube conduit system during heating cycles is controlled based ona pressure in the system.
 28. The method of claim 24, further comprisinghumidifying air in a space to be heated using condensate from the steamdelivered to the radiator.
 29. The method of claim 24, furthercomprising cooling a space by transferring cold air into thetube-in-tube conduit system to be delivered to one or more cold airregisters, the one or more cold air registers delivering the cold air tothe space to be cooled.
 30. The method of claim 29, further comprisingdirecting the steam to provide energy to a cold air source.